This research is aimed at specifically demonstrating the potential of LCMS-MS as a tool for the structural elucidation and identification of metabolites from in vitro reaction mixtures. Identification of such metabolites will lead to a better understanding of pathways associated with the carcinogenesis. It will also demonstrate the power of LCMS and LCMS-MS for the analysis of complex mixtures containing high molecular weight metabolites. This research is also aimed at the applicability of collision induced reactions in a tandem mass spectrometer (MS/MS) for determining adduct formation and site specificity of PAH/NPAH metabolites and degradation products to DNA. It will also establish what problems and solutions there are in identifying metabolites/degradation products of PAHs, NPAHs and other compounds of environmental concern can be readily separated, detected and identified by liquid chromatography mass spectrometry (LCMS) or liquid chromatography mass spectrometry-mass spectrometry (HPLC-MS- MS). In proving the applicability of LCMS-MS to the identification of metabolites, it will also seek to identify those metabolites that have been previously unidentified from in vitro reactions of PAHs and NPAHs. Identification of these metabolites would provide additional input into the overall understanding of the metabolism of these species to active carcinogens. A series of PAHs will be metabolized, in vitro using liver microsomes, to produce metabolites and/or adducts. The metabolites and adducts will be separated from the reaction mixture. These metabolites will be further separated and then analyzed in a tandem quandrupole mass spectrometer coupled to a liquid chromatograph using an electrospray of thermospray sample introduction interface. Mass selection occurs in the first quadrupole, ie. separation, collision with an energetic inert gas occurs in the second, i.e. fragmentation, and complete mass spectral analysis occurs in the third. The results of which will permit identification of the metabolite in a complex mixture.